Determinação eletroquímica de amoxicilina e nimesulida usando um eletrodo de carbono vítreo modificado com carbon black em um filme de DHP

The carbon black (CB )is a nanostructured carbon nanomaterial, which has been widely used for the development of electrochemical sensors. This material canfacilitate electron transfer processes, causing significant increase of analytical signal1. Therefore, we explored a glassy carbon electrode (GCE) modified with carbon black (CB) within a dihexadecyl hydrogen phosphate (DHP) film as electrode materialto developinga simple and low cost analytical method for the simultaneous determination ofamoxicillin (AMX) and nimesulide (NIM)in biological samples. In Fig. 1, is shownthe voltammogramobtainedfor 5x10-4 mol L−1 AMX and 1x10-4mol L−1 NIMat GCE (–), an dat CB-DHP/GCE (–) in 0.2 mol L−1 phosphate buffer pH 7.0 solution at a scan rate of 50 mV s–1). As can been see from this figure,awell-defined oxidation peak in ca.730mV for AMX and 900mVfor NIM was obtained atCB-DHP/GCE, however using a GCE was obtained oxidation peak for NIM in937.0 mV and for AMX there was no oxidation process. The analytical signal was substantially increased and the oxidation potentials decreased, when CB-DHP/CGE was used, characteristic of an electrocatalytic effect. This effect suggestsa more favourable electrochemical interaction of these analytesat the electrode surface and enhanced of electron transfer kinetics. The obtained values of the heterogeneous electron transfer rate constant (k0) were 6.8x10-3, and 2.0x10-2cm s-1 for AMX and NIM at CB-DHP/GCE, respectively. After optimizing, the supporting electrolyte, pH andthe parameters of the SWV(f= 50 Hz; a= 20 mV; ∆E= 5mV), the analytical curvesfor AMX and NIM were linear in concentration ranges from 2.0 to 20.0 μmol L−1 and 0.30 to 3.0 μmol L−1 with detection limit of 0.12μmol L−1 and 0.016 μmol L−1 for AMX and NIM, respectively. The CB-DHP/GCE sensor was successfully applied for determination these analytes in different biological samples by SWV.The proposed method was considered very attractive, since there are no electroanalytical methods described in the literature for the simultaneous determination of these drugs.